Multiple Constraints at the Level of TCR Rearrangement Impact V 14i NKT Cell Development

CD1d-restricted NKT cells that express an invariant V 14 TCR represent a subset of T cells implicated in the regulation of several immune responses, including autoimmunity, infectious disease, and cancer. Proper rearrangement of V 14 with the J 18 gene segment in immature thymocytes is a prerequisite to the production of a TCR that can be subsequently positively selected by CD1d/self-ligand complexes in the thymus and gives rise to the NKT cell population. We show here that V 14 to J rearrangements are temporally regulated during ontogeny providing a molecular explanation to their late appearance in the thymus. Using mice deficient for the transcription factor ROR and the germline promoters T earlyand J 49, we show that developmental constraints on both V and J usage impact NKT cell development. Finally, we demonstrate that rearrangements using V 14 and J 18 occur normally in the absence of FynT, arguing that the effect of FynT on NKT cell development occurs subsequent to -chain rearrangement. Altogether, this study provides evidence that there is no directed rearrangement of V 14 to J 18 segments and supports the instructive selection model for NKT cell selection. The Journal of Immunology, 2007, 179: 2228–2234.